The long range goal of this project is to understand how epinephrine-stimulation of Alpha 1- adrenergic receptors leads to calcium movement. It is known that Alpha 1- adrenergic stimulation mediates its acute physiological response in liver, glycogenolysis, via a rise in intracellular calcium. An important technical difficulty that hinders obtaining an understanding of the mechanism by which the intracellular calcium concentration, [CA++]j, rises is that a convenient and rapid assay for [CA++]i in hepatocytes is not available. The immediate goal of this project is the development of a method to monitor [CA++]i. This will be accomplished by measuring the dependence of a calcium-dependent potassium permeability, PK, Ca, on calcium concentration. The approach will be to determine 1) The calcium-dependent potassium permeability in vesicles isolated from plasma membrane of guinea pig hepatocytes and 2) single channel properties of the calcium-sensitive potassium channel using patch voltage clamp. By patch clamping whole hepatocytes, the epinephrine stimulated K+ current will be obtained. This, combined with the calibrated CA++-dependent K+ permeability, allows the internal CA++ concentration to be monitored, utilizing the advantages of electrophysiological techniques. Further, by introducing into the cell, via a patch pipette, agents which are known to cause release of CA++ from internal organelles in liver cells, an approach to study the transduction of plasma membrane signalling to internal organelles will be developed. Thus control and measurement of internal calcium will be possible via the same patch electrode.